Tool for Grinding Toothed Workpieces Having Collision Contours

ABSTRACT

A tool for generating tooth systems by grinding when the maximum tool diameter is limited by collision contours on the workpiece has a dressable grinding tool that is tightly connected to the tool holder. In one preferred arrangement, the dressable grinding tool is glued on the tool holder.

The invention relates to a tool for grinding toothed workpieces usingdressable grinding tools which were optimized with regard to the maximumtool diameter by collision surfaces, like interference contours orlimitations from the preprocessing, such as tool run-out.

Known tools for generating grinding of tooth systems always have a toolholding mandrel or flange by means of which the tool is held in thegrinding machine. This mandrel/flange requires a certain minimumdiameter in order to have the necessary stability. The tool(s) is(are)fitted on this mandrel/flange and generally fastened to themandrel/flange by laterally arranged fastening elements. So that acollision between the tool and holding mandrel/flange does not occurduring grinding, the usable tool diameter only begins after this region.A certain minimum tool diameter results due to this design principle anddue to the coating thickness necessary in the abrasive coating for aneconomical grinding process.

Modern transmissions contain, in addition to the classic gears with bore(“bored workpieces”), input-, intermediate-, and drive shafts as well,which have one or more toothings which are directly connected to theshaft and/or come from a raw material. A characteristic of thesecomponents is a workpiece geometry that has so-called collision teeth,i.e. a further toothing, a shaft collar, another interference contour isnext to the toothing to be processed, or the toothing does not end in anend surface but instead runs out with a radius. This must be consideredwith regard to the design of the toothing tool already during machiningbefore heat treatment (roughing with hob or form cutter). During thehard-fine machining necessary after hardening, the tool diameter mayoften only have maximally the same diameter as during the machiningbefore heat treatment.

In general, these workpieces are processed after the heat treatmentusing the following hard-fine machining processes:

1. Generating grinding using electrically coupled CBN worm grindingwheels

2. Profile grinding using electrically coupled CBN profile grindingwheels

3. Gear honing and

4. Generating grinding using dressable cutting material (aluminum oxide,CBN or similar)

5. Profile grinding using dressable cutting material (aluminum oxide,CBN or similar)

If dressable tools are used (methods 4 & 5), then, due to the collisionsituation at grinding wheels and worm grinding wheels and a conventionaltool design, the installation space is lacking for the necessary coatingthickness which is required in order to always generate new, fresh, easyto cut grinding tool surfaces, even during multiple dressing of smallcutting material coatings. Due to this circumstance, dressable profile-and generating worm grinding wheels are not economical in thisapplication, even though these cutting materials are used extremelysuccessfully in “collision-free” tooth systems.

For this reason, these tooth systems have often been hard-fine processedusing methods 1-3 up until now. This is due to economic reasons andbecause tools made from dressable cutting materials can be more easilyre-profiled; however, a process with dressable tools would be desirable.It is, however, necessary for this purpose that a certain minimumcoating thickness is realized in order to obtain an economically usabletool. At the same time, the tool mandrel requires a minimum diameter sothat the necessary stability and stiffness is realized. These twolimiting conditions define or delimit the possible radial installationspace for the tool.

DE 101 04 410 A1 discloses a tool for generating grinding of toothsystems during which the grinding tool consists of a bearing ring and anabrasive body which is fitted on a conical mounting flange. By thismeans, the grinding tool is fixed without play. The deformationresistance of the bearing ring is thereby greater than that of theabrasive body. Due to this embodiment, displacements and deformations ofthe worm grinding wheel caused by centrifugal forces are minimized.Disadvantageous in this embodiment are the spatial requirements requiredin order to accommodate all function elements in the tool and at thesame time guarantee the necessary stability of the holder.

WO 94/19135 discloses a single-part galvanically-coated tool having twodifferent portions. These two portions are coated with hard materials inorder to undertake different grinding tasks during the hard-finemachining process. The grinding tool comprises a conical mounting sleevewith which it is fitted on the round tool mandrel and tightened. Thisembodiment also requires a certain minimum height for the tool. Inconnection with a stable round mandrel for the tool, this results in acertain minimum tool diameter. In this embodiment of the tool, the tooldiameter and/or the coating thickness are no longer changed thereby,since no dressing of the abrasive coating takes place. If this tool isworn out, it must first be decoated in order to be subsequently newlyrecoated. Disadvantageous in this embodiment is that changes to theprofile shape of the grinding tool can only be generated during themanufacture thereof. During the hard-fine machining, such changes orre-profilings are no longer possible due to the low coating thickness ofthe abrasive material. This is only possible using dressable grindingtools.

DE 10 2004 020 364 A1 likewise describes a tool for generating grindingof tooth systems having a multi-part grinding tool with dressableabrasive bodies. In this case, a multi-part tool is described in whichdifferent abrasive bodies are clamped on a common base mandrel.

It would be desirable to make a new type of tool available to a personskilled in the art for economical hard-fine machining of workpieceshaving an interference contour which is next to the toothing to beprocessed.

A use of grinding tools with dimensions according to the prior art is nolonger possible for tooth systems of this type due to reasons ofcollisions. If a tool with a reduced outer diameter is used, which has,however, a conventional design, then the remaining residual wallthickness of the dressable abrasive coating is reduced to such an extentthat an economical use is no longer possible.

It is thus the object of the present invention to configure thestructure of the grinding tool such that the necessary stiffness of theholding mandrel is guaranteed in order to generate the required grindingquality and at the same time the necessary coating thickness is providedfor an economical number of dressing cycles.

This problem is solved by a tool having the features of claim 1.

The essential aspect of the invention is a tool for generating grindinghaving a dressable worm grinding wheel with a small outer diameter and acoating thickness necessary for a repeated dressing cycle. This isachieved, in contrast to conventional tool design, in that the abrasivecoating is no longer fitted on and tightened onto the tool holder, whichconsists in particular of a tool mandrel or a mounting sleeve, butinstead the abrasive coating is glued directly to the tool holder, inparticular the tool mandrel or mounting sleeve.

Due to this design, the stops arranged laterally adjacent to the tooland the previously necessary fastening and fixing units are not needed.In addition, the worm grinding wheel sleeve, on which the worm grindingwheel is usually glued in conventional tool design, is also not needed,in particular if the grinding tool is composed of grinding wheelsegments.

Due to this development, significantly smaller tool diameters can berealized for dressable tools and thus enable an economical and flexiblemachining of workpieces having collision contours, even while usingdressable grinding tools. Due to the segmented design of the grindingtool, tool widths, which cannot be realized using a single-part tooldesign, can be realized. The maximum width of the worm blank is known tobe limited by the production method thereof. Beginning at a certainratio of worm width to material thickness, the worm blank can no longerpress with the necessary homogeneity. This tool would then have adisadvantage, e.g. due to different grinding behavior across the widththereof or different absorption capacity for coolants, which would againlead to problems during balancing of the tool.

Further advantageous embodiments of the method are the subject matter ofthe claims subsequently dependent on the main claim.

The glued tool can again be combined with further tools, in casemultiple tooth systems should be processed serially on a workpiece, inthe case that a toothing should be processed with different grindingprocesses, e.g. generating grinding and profile grinding. Further, it isalso possible to machine different grinding processes, like toothinggrinding and grinding outer diameters, surfaces, grooves, or slots witha tool according to the invention. A combination of dressable andnon-dressable tools is also possible in order to machine one or moretooth systems of surfaces.

A combination is also conceivable, made of a dressable grinding tool tomachine a collision contour together with a non-dressable tool. By thismeans, a still smaller collision contour can be machined, at whichmachining using a dressable tool is no longer economically presentable.This enables according to the invention e.g. the machining of toothsystems that up until now could not be economically processed usinggenerating grinding.

A further application of these tools is for workpieces in which thetooth system does not end in an end face, but rather in a tool run-out.In this case, the diameter of the grinding tool may not be larger thanthe diameter from the preprocessing.

Further features, details, and advantages of the invention will bedescribed by means of embodiments depicted schematically in thedrawings. As seen in:

FIG. 1: a grinding tool according to the prior art,

FIG. 2: a grinding tool engaged with a workpiece having a collisioncontour,

FIG. 3: embodiment of grinding tools according to the invention, and

FIG. 1 shows a grinding tool according to the prior art. One or moregrinding tools 10 are mounted on a tool mandrel 20 having double-sidedmounting surfaces 21 for mounting the tool in the machine head of atooth grinding machine (not depicted here), and are fixed on the toolmandrel by fixing with a clamping cover or clamping unit 30.

FIG. 2 now shows a perspective view of a grinding tool 60 according tothe invention. By means of the double toothing 50 depicted, thedifficulty can also be seen which leads to a limit of the diameter ofthe grinding tool. Based on the helical gearing and the slanted positionof the grinding tool necessitated thereby in the engaged position, thetool diameter may not exceed a certain diameter, since otherwise thiswould lead to a collision of the tool with the lower toothing.

The design of the worm grinding wheel can likewise be seen, which designconsists of a plurality of individual segments 65 which are gluedradially to the outer circumference of the tool mandrel.

FIGS. 3 a to 3 e exemplarily show different embodiments of the toolarrangement with one or more grinding tools which are engaged with aworkpiece having a collision contour, in the example of the doubletoothing 50 from FIG. 2. The view is depicted from the direction of amachine head in the direction toward the workpiece to be machined.

FIG. 3 a shows a dressable worm grinding wheel 60 which consists ofcircular segments 65 glued radially to the outer diameter on the toolmandrel 40. The slanted position of the tool is determined, among otherreasons, by the helix angle and the tool design.

A dressable worm grinding wheel is likewise shown in FIG. 3 b, whichworm grinding wheel in this case is constructed of a plurality of ringsections 66 which again are glued to the tool mandrel 40.

The combination tool shown in FIG. 3 c consists of a dressable wormgrinding wheel 62 composed of individual segments glued to a toolmandrel 41, and a mounted grinding wheel 63 which can be implemented asdressable or non-dressable.

The tool arrangement with two worm grinding wheels, as is shown in FIG.3 d, consists likewise of a glued on worm grinding wheel 61 and amounted worm grinding wheel 64 that is implemented as dressable ornon-dressable, and which is fixed to a tool mandrel 42 in this case by aclamping cover 44.

FIG. 3 e shows a tool arrangement with a single-sided mounting cone forthe tool in the tool holder.

Exemplary workpieces, as they can be machined according to the inventionusing a grinding tool, are depicted in FIG. 4.

1-11. (canceled)
 12. A tool for grinding tooth systems in which themaximum tool diameter is limited by collision contours on a workpiece,comprising: a tool holder, and a grinding tool mounted on said toolholder, wherein the grinding tool is a dressable grinding tool that istightly connected to the tool holder by gluing.
 13. The tool accordingto claim 12, wherein the dressable grinding tool consists of at leastone single-part sleeve that is glued on the tool holder.
 14. The toolaccording to claim 12, wherein the dressable grinding tool consists ofat least two circular segments that are glued radially on the toolholder.
 15. The tool according to claim 12, wherein the tool holderconsists of a tool mandrel or a mounting sleeve.
 16. The tool accordingto claim 12, wherein the dressable grinding tool has at least tworegions that have different coating specifications, different grains,different binders, and/or different physical or chemical bindercharacteristics, and are designed with regard to use as roughing orfinishing tools for at least one toothing.
 17. The tool according toclaim 16, wherein the dressable grinding tool has at least two regionsthat have different screw geometries, wherein the regions arerespectively divided into a roughing region and a finishing region, andwherein the regions have said different coating specifications, saiddifferent grains, said different binders and/or said different physicalor chemical binder characteristics, in order to grind two or moredifferent tooth systems.
 18. The tool according to claim 12, wherein thetool holder is a tool holding mandrel that has at least two regions,wherein at least one of said two regions is a region in which adressable grinding tool can be glued, and wherein the other of the tworegions is a region in which a dressable or non-dressable grinding toolcan be clamped or fastened.
 19. The tool according to claim 12, whereinthe tool holder is a tool holding mandrel that has at least two regions,and wherein said grinding tool is one of several grinding tools,including a dressable worm grinding wheel and at least one furthergrinding tool that is a dressable or non-dressable grinding tool in theform of a grinding wheel, a set of grinding wheels, or a worm grindingwheel.
 20. The tool according to claim 12, wherein the tool holder is atool holding mandrel that has at least two regions, and wherein saidgrinding tool is one of several grinding tools, including a grindingwheel or a set of grinding wheels and at least one further grinding toolthat is a dressable or non-dressable grinding tool in the form of agrinding wheel, a set of grinding wheels, or a worm grinding wheel. 21.The tool according to claim 12, wherein the tool holder is a toolholding mandrel that has at least one tool for tooth grinding, whereinsaid grinding tool is one of several grinding tools, including adressable worm grinding wheel, a grinding wheel, or set of grindingwheels, and at least one further grinding tool that is a dressable ornon-dressable grinding tool in the form of a grinding wheel or a set ofgrinding wheels, in order to machine non-toothed geometries, diameters,surfaces, grooves, or slots.
 22. The tool arrangement according to claim12, wherein the tool holder is a tool holding mandrel that has one ortwo interfaces for mounting the tool mandrel in a machining head. 23.The tool according to claim 13, wherein the tool holder consists of atool mandrel or a mounting sleeve.
 24. The tool according to claim 13,wherein the dressable grinding tool has at least two regions that havedifferent coating specifications, different grains, different binders,and/or different physical or chemical binder characteristics, and aredesigned with regard to use as roughing or finishing tools for at leastone toothing.
 25. The tool according to claim 13, wherein the toolholder is a tool holding mandrel that has at least two regions, whereinat least one of said two regions is a region in which a dressablegrinding tool can be glued, and wherein the other of the two regions isa region in which a dressable or non-dressable grinding tool can beclamped or fastened.
 26. The tool according to claim 13, wherein thetool holder is a tool holding mandrel that has at least two regions, andwherein said grinding tool is one of several grinding tools, including adressable worm grinding wheel and at least one further grinding toolthat is a dressable or non-dressable grinding tool in the form of agrinding wheel, a set of grinding wheels, or a worm grinding wheel. 27.The tool according to claim 13, wherein the tool holder is a toolholding mandrel that has at least two regions, and wherein said grindingtool is one of several grinding tools, including a grinding wheel or aset of grinding wheels and at least one further grinding tool that is adressable or non-dressable grinding tool in the form of a grindingwheel, a set of grinding wheels, or a worm grinding wheel.
 28. The toolaccording to claim 13, wherein the tool holder is a tool holding mandrelthat has at least one tool for tooth grinding, wherein said grindingtool is one of several grinding tools, including a dressable wormgrinding wheel, a grinding wheel, or set of grinding wheels, and atleast one further grinding tool that is a dressable or non-dressablegrinding tool in the form of a grinding wheel or a set of grindingwheels, in order to machine non-toothed geometries, diameters, surfaces,grooves, or slots.
 29. The tool arrangement according to claim 13,wherein the tool holder is a tool holding mandrel that has one or twointerfaces for mounting the tool mandrel in a machining head.
 30. Thetool according to claim 14, wherein the tool holder consists of a toolmandrel or a mounting sleeve.
 31. The tool according to claim 14,wherein the dressable grinding tool has at least two regions that havedifferent coating specifications, different grains, different binders,and/or different physical or chemical binder characteristics, and aredesigned with regard to use as roughing or finishing tools for at leastone toothing.